Mini Cooper exhaust flap issue

I had something similar with my Cooper. Louder exhaust, especially on cold starts. Check the exhaust flaps and especially the flap motor. Sometimes they get stuck or the motor burns out. An exhaust blockage can also cause similar symptoms, but less likely. Do you have any error codes?

Could you provide more detail regarding which exhaust components I should inspect, and how to identify a defective flap motor?

The flap actuator is the most common culprit. You'll find it near the exhaust. Check the wiring first; sometimes it's just a loose connection. If the wiring is fine, try manually moving the exhaust flaps. If they're stuck, that's your problem. If they move freely, the flap motor is probably dead. I ended up going to a workshop for mine; they confirmed the defective motor.

The flap actuator was indeed defective as initially suspected. Repair cost 190€. Thank you for the advice.